1. Field of the Invention
The present invention relates generally to a data communication system and, more specifically, to a the radio communication system for exchanging data, such as movie pictures, still pictures, and voice composite with the pictures, by modulation of radio frequencies.
2. Description of the Prior Art
When linking two or more data communication equipments, in general, each equipment has a link interface for communication with other equipment, and connecting the link interface of each equipment to opposite ends of a cable results in wire link of the equipments.
On the other hand, a contemporary data communication system between two communication equipments that perform bi-directional communication through radio communication circuit confirms the copy ability of a signal by increasing signal strength of the transmitter when there is no reply to the signal transmitted from the transmitter. (E.g. laid-open disclosure public patent bulletin 2001-17417)
For the case of linking through a cable, for example connection of a personal computer (PC) to a Liquid Crystal Display (LCD) Projector, a cable connecting a PC and an LCD projector has a fixed length so that the position of the LCD projector defines that of the PC. Especially, a LCD projector will be set away from a projection screen, and then, the PC has to be set away from the projection screen when high magnification is employed during display.
For the case of Current Radio Link between a PC and a LCD projector, increasing a signal strength may help readability of the signal while no reply is received for the transmitted signals. Increasing the signal strength may cause inadequate radio power shown a reply is received. Excess signal strength causes the reach of a radio wave in excess of what the reach should be, and the problem of concealing confidential information arises if a person copies the transmitted information by catching the radio wave far and out of the room of transmission. The sophisticated signal treatment of adding scramble signals has to be employed in order to avoid copy of the information.